The present invention relates to a semiconductor device with a booster part and a booster. For example, it relates to a technique useful in application to a driver IC (Integrated Circuit) of a display panel.
To raise a voltage of an external power source, a charge-pump circuit may be used. For instance, a liquid crystal driver used to drive a liquid crystal display panel may use a boost voltage to select pixels of the liquid crystal panel by display line. Examples of a literature which describes a charge-pump circuit include the Japanese Unexamined Patent Application Publication No. JP-A-2010-256403.
In the case of materializing a charge-pump circuit by an on-chip circuit of a semiconductor device, externally-mounted elements are used for a stabilization capacitance and a pumping capacitance. A charge-pump circuit alternately switches a capacitive electrode of one of pumping capacitances between first and second voltages and in parallel, periodically applies a third voltage to a capacitive electrode of the other pumping capacitance. The charge-pump circuit lifts up the third voltage thus applied each time the input of the pumping capacitance is switched from the first voltage to the second voltage, thereby successively supplying the resultant boost voltage to a stabilization capacitance through an output MOS (metal-oxide-semiconductor) switch circuit. In this way, a boost voltage resulting from the increase in voltage to a voltage representing the sum of the second voltage and the third voltage can be obtained.
In this charge-pump circuit, a boost voltage is formed on the capacitive electrode of the other pumping capacitance eventually. Therefore, a MOS switch circuit serving to apply the third voltage to the capacitive electrode, and the output MOS switch circuit have a withstand voltage comparable to a voltage representing the sum of the second voltage and the third voltage. That is, for each of such MOS switch circuits, a high-voltage MOS switch circuit larger, in withstand voltage, than a middle-voltage MOS switch circuit serving to alternately apply the first and second voltages before boosting to the one pumping capacitance should be used. A MOS switch element larger in withstand voltage has a larger on-resistance. To reduce the on-resistance, it is necessary to increase the transistor size, thereby widening the width of a gate.